The earth's crust is made of up separate plates that ride atop a sea of magma. These plates are constantly shifting and interacting. The phenomena that affect the size and shape of the Earth's continents and ocean basins are subtle and occur over hundreds of thousands of years. (Image source: GIS-based plate boundaries, ETOPO2 global elevation data).
Heard of geodesy? These videos from NOAA's National Geodetic Survey offer a deep dive into the science of knowing where you – and everything else is in the world!
The National Science Teaching Association (NSTA) includes this resource in its database. NSTA provides educators and students access to Web-based, educationally appropriate science content that has been formally evaluated by master teachers.